Method and device for receiving downlink signal in wireless communication system

ABSTRACT

A method for receiving a downlink signal in a wireless communication system according to an embodiment of the present invention is performed by a terminal, and may comprise the steps of: receiving, from a base station, a dynamic change configuration into a predetermined transmission scheme related to a short transmission time interval (sTTI)-based downlink operation; when the dynamic change configuration is received, detecting a downlink control information format including a field related to the dynamic change; and when a value of the field indicates the predetermined transmission scheme, receiving a signal on a downlink data channel according to the predetermined transmission scheme.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/612,669, filed on Nov. 11, 2019, which is a National Stageapplication under 35 U.S.C. § 371 of International Application No.PCT/KR2018/005554, filed on May 15, 2018, which claims the benefit ofU.S. Provisional Application No. 62/655,739, filed on Apr. 10, 2018,Korean Application No. 10-2018-0039926, filed on Apr. 5, 2018, U.S.Provisional Application No. 62/651,242, filed on Apr. 1, 2018, U.S.Provisional Application No. 62/571,266, filed on Oct. 12, 2017, and U.S.Provisional Application No. 62/506,563, filed on May 15, 2017. Thedisclosures of the prior applications are incorporated by reference intheir entirety.

TECHNICAL FIELD

The present disclosure relates to a wireless communication system, andmore particularly, to a method and apparatus for receiving a downlinksignal, which support a plurality of transmission time intervals (TTIs),a plurality of processing times, or a plurality of numerologies.

BACKGROUND ART

The latency of packet data is one of important performance metrics. Toreduce the latency of packet data and provide faster Internet access toend users is one of challenging issues in designing the next-generationmobile communication system called new radio access technology (new RAT)as well as long term evolution (LTE).

The present disclosure is intended to deal with downlink signalreception or transmission techniques in a wireless communication systemsupporting latency reduction.

DISCLOSURE Technical Problem

The present disclosure relates to downlink reception at a user equipment(UE) with a plurality of transmission time intervals (TTIs), a pluralityof processing times, or a plurality of numerologies in a carrieraggregation (CA) system.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present disclosure are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present disclosure could achieve will be more clearlyunderstood from the following detailed description.

Technical Solution

In an aspect of the present disclosure, a method for receiving downlinksignals in a wireless communication, the method performed by a terminal,includes receiving, from a base station, a configuration of dynamicchange to a predetermined transmission scheme related to a shorttransmission time interval (sTTI)-based downlink operation, whenreceiving the configuration of the dynamic change, detecting a downlinkcontrol information format including a field related to the dynamicchange, and when a value of the field indicates the predeterminedtransmission scheme, receiving signals on a downlink data channelaccording to the predetermined transmission scheme.

Additionally or alternatively, the configuration of the dynamic changemay be configured per transmission time interval (TTI) length.

Additionally or alternatively, the configuration of the dynamic changemay be configured irrespective of a transmission mode related to thesTTI-based downlink operation.

Additionally or alternatively, the predetermined transmission scheme maybe transmit diversity.

Additionally or alternatively, the method may further include reporting,to the base station, a terminal capability as to whether the dynamicchange to the predetermined transmission scheme is supported.

Additionally or alternatively, the terminal capability reporting may bedefined per TTI length.

Additionally or alternatively, the downlink control information formatmay schedule downlink data channels in a plurality of TTIs, and hybridautomatic repeat request (HARQ)-acknowledgment (ACK) responses for thedownlink data channels in the plurality of TTIs may be transmittedindividually at timings corresponding to the respective downlinkchannels in the plurality of TTIs.

Additionally or alternatively, the downlink control information formatmay schedule downlink data channels in a plurality of TTIs, and HARQ-ACKresponses for the downlink channels in the plurality of TTIs may betransmitted by bundling or aggregation.

Additionally or alternatively, the HARQ-ACK responses may be transmittedin resources determined by a lowest control channel element (CCE) indexof the downlink control information format or resources spaced fromresources linked to states of an ACK/NACK resource indicator (ARI) fieldby a predetermined offset.

Additionally or alternatively, a resource block set for monitoring thedownlink control information format, an aggregation level to be used inthe resource block set for monitoring the downlink control informationformat, and/or the number of monitoring candidates may be configured.

In another aspect of the present disclosure, a terminal for receivingdownlink signals in a wireless communication system includes a receiverand transmitter, and a processor configured to control the receiver andthe transmitter. The processor is configured to receive, from a basestation, a configuration of dynamic change to a predeterminedtransmission scheme related to an sTTI-based downlink operation, whenreceiving the configuration of the dynamic change, detect a downlinkcontrol information format including a field related to the dynamicchange, and when a value of the field indicates the predeterminedtransmission scheme, receive signals on a downlink data channelaccording to the predetermined transmission scheme.

Additionally or alternatively, the configuration of the dynamic changemay be configured on a TTI basis.

Additionally or alternatively, the configuration of the dynamic changemay be configured irrespective of a transmission mode related to thesTTI-based downlink operation.

Additionally or alternatively, the predetermined transmission scheme maybe transmit diversity.

Additionally or alternatively, the processor may be configured toreport, to the base station, a terminal capability as to whether thedynamic change to the predetermined transmission scheme is supported.

Additionally or alternatively, the terminal capability reporting may bedefined on a TTI length basis.

Additionally or alternatively, the downlink control information formatmay schedule downlink data channels in a plurality of TTIs, and HARQ-ACKresponses for the downlink data channels in the plurality of TTIs may betransmitted individually at timings corresponding to the respectivedownlink channels in the plurality of TTIs.

Additionally or alternatively, the downlink control information formatmay schedule downlink data channels in a plurality of TTIs, and HARQ-ACKresponses for the downlink channels in the plurality of TTIs may betransmitted by bundling or aggregation.

Additionally or alternatively, the HARQ-ACK responses may be transmittedin resources determined by a lowest CCE index of the downlink controlinformation format or resources spaced from resources linked to statesof an ACK/NACK resource indicator (ARI) field by a predetermined offset.

Additionally or alternatively, a resource block set for monitoring thedownlink control information format, an aggregation level to be used inthe resource block set for monitoring the downlink control informationformat, and/or the number of monitoring candidates may be configured.

The above technical solutions are merely some parts of the examples ofthe present disclosure and various examples into which the technicalfeatures of the present disclosure are incorporated can be derived andunderstood by persons skilled in the art from the following detaileddescription of the present disclosure.

Advantageous Effects

According to the examples of the present disclosure, downlink receptionmay be efficiently performed.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present disclosure are not limited to whathas been particularly described hereinabove and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure, illustrate examples of the disclosureand together with the description serve to explain the principle of thedisclosure.

FIG. 1 illustrates the structure of a radio frame used in a wirelesscommunication system.

FIG. 2 illustrates the structure of a downlink (DL)/uplink (UL) slot ina wireless communication system.

FIG. 3 illustrates the structure of a DL subframe used in a 3^(rd)generation partnership project long term evolution (3GPPLTE)/LTE-advanced (LTE-A) system.

FIG. 4 illustrates the structure of a UL subframe used in the 3GPPLTE/LTE-A system.

FIG. 5 illustrates reduction of a transmission time interval (TTI)length due to reduction of a user-plane latency.

FIG. 6 illustrates an example of a plurality of shortened TTIs (sTTIs)configured in one subframe.

FIG. 7 illustrates the structures of DL subframes including sTTIs of aplurality of lengths (a plurality of numbers of symbols).

FIG. 8 illustrates the structures of DL subframes including 2-symbol or3-symbol sTTIs.

FIG. 9 is a block diagram of devices for implementing the embodiment(s)of the present disclosure.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the exemplary examples of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. The detailed description, which will be givenbelow with reference to the accompanying drawings, is intended toexplain exemplary examples of the present disclosure, rather than toshow the only examples that can be implemented according to thedisclosure. The following detailed description includes specific detailsin order to provide a thorough understanding of the present disclosure.However, it will be apparent to those skilled in the art that thepresent disclosure may be practiced without such specific details.

In some instances, known structures and devices are omitted or are shownin block diagram form, focusing on important features of the structuresand devices, so as not to obscure the concept of the present disclosure.The same reference numbers will be used throughout this specification torefer to the same or like parts.

In the present disclosure, a user equipment (UE) may be a fixed ormobile device. Examples of the UE include various devices that transmitand receive user data and/or various kinds of control information to andfrom a base station (BS). The UE may be referred to as a terminalequipment (TE), a mobile station (MS), a mobile terminal (MT), a userterminal (UT), a subscriber station (SS), a wireless device, a personaldigital assistant (PDA), a wireless modem, a handheld device, etc. Inaddition, in the present disclosure, a BS generally refers to a fixedstation that performs communication with a UE and/or another BS, andexchanges various kinds of data and control information with the UE andanother BS. The BS may be referred to as an advanced base station (ABS),a node-B (NB), an evolved node-B (eNB), a base transceiver system (BTS),an access point (AP), a processing server (PS), etc. In describing thepresent disclosure, a BS will be referred to as an eNB.

In the present disclosure, a node refers to a fixed point capable oftransmitting/receiving a radio signal through communication with a UE.Various types of eNBs may be used as nodes irrespective of the termsthereof. For example, a BS, a node B (NB), an e-node B (eNB), apico-cell eNB (PeNB), a home eNB (HeNB), a relay, a repeater, etc. maybe a node. In addition, the node may not be an eNB. For example, thenode may be a radio remote head (RRH) or a radio remote unit (RRU). TheRRH or RRU generally has a lower power level than a power level of aneNB. Since the RRH or RRU (hereinafter, RRH/RRU) is generally connectedto the eNB through a dedicated line such as an optical cable,cooperative communication between RRH/RRU and the eNB can be smoothlyperformed in comparison with cooperative communication between eNBsconnected by a radio line. At least one antenna is installed per node.The antenna may mean a physical antenna or mean an antenna port or avirtual antenna. A node is also referred to as a point. Compared to aconventional centralized antenna system (CAS) (i.e., a single-nodesystem) in which antennas are concentrated in an eNB and controlled byone eNB controller, a plurality of nodes are generally located apartfrom each other by a predetermined distance or larger in a multi-nodesystem. The plurality of nodes may be managed by one or more eNBs or eNBcontrollers which schedule data to be transmitted/received through eachnode. Each node may be connected to an eNB or eNB controller managingthe node by cable or a dedicated line. In the multi-node system, thesame or different cell identifies (IDs) may be used for signaltransmission/reception to/from the plurality of nodes. If the pluralityof nodes has the same cell ID, each of the nodes operates as a set ofsome antennas in one cell. If the nodes have different cell IDs in themulti-node system, this multi-node system may be regarded as amulti-cell (e.g., macro-cell/pemto-cell/pico-cell) system. If multiplecells formed by the plurality of nodes, respectively are overlaid witheach other according to their coverages, a network constructed with themultiple cells is called a multi-tier network. The cell ID of an RRH/RRUand the cell ID of an eNB may be the same or different. If the RRH/RRUand the eNB use different cell IDs, both of the RRH/RRU and the eNBoperate as independent BSs.

In a multi-node system of the present disclosure as described below, oneor more eNBs or eNB controllers connected to a plurality of nodes maycontrol the nodes to enable all or a part of the nodes to simultaneouslytransmit or receive signals to and from a UE. Although there aredifferences between multi-node systems in terms of the entity andimplementation of each node, the multi-node systems are also differentfrom a single-node system (e.g., a CAS, a legacy MIMO system, a legacyrelay system, a legacy repeater system, or the like) in that a pluralityof nodes participate together in providing a communication service to aUE in predetermined time-frequency resources. Accordingly, examples ofthe present disclosure pertaining to a method of performing datacooperative transmission by means of all or a part of a plurality ofnodes are applicable to various types of multi-node systems. Forexample, while a node generally refers to an antenna group apart fromanother node by a predetermined distance or larger, the followingexamples of the present disclosure are also applicable even when a noderefers to any antenna group irrespective of the distance between nodes.For example, for an eNB including X-pol (cross-polarized) antennas, theexamples of the present disclosure may be applied with the appreciationthat the eNB controls a node with H-pol antennas and a node with V-polantennas.

A communication technique in which signals are transmitted/receivedthrough a plurality of transmission (Tx)/reception (Rx) nodes, signalsare transmitted/received through at least one node selected from aplurality of Tx/Rx nodes, or a node transmitting a DL signal isdifferent from a node receiving a UL signal is called multi-eNB MIMO orcoordinated multi-point Tx/Rx (CoMP). Among these schemes forcooperative communication between nodes, cooperative transmissionschemes are largely classified into joint processing (JP) and schedulingcoordination. JP may further be classified into joint transmission(JT)/joint reception (JR) and dynamic point selection (DPS), whereasscheduling coordination may further be classified into coordinatedscheduling (CS) and coordinated beamforming (CB). DPS is also referredto as dynamic cell selection (DCS). Compared to the cooperativecommunication schemes, when JP is performed among cooperativecommunication schemes between nodes, various communication environmentsmay be formed. Among the JP schemes, a plurality of nodes transmits thesame streams to a UE in JT, and a plurality of nodes receive the samestream from a UE in JR. The UE/eNB recovers the stream by combining thereceived signals. In view of transmission of the same stream from/to aplurality of nodes in JT/JR, the reliability of signal transmission maybe increased by transmit diversity. Among the JP schemes, DPS is acommunication scheme in which a signal is transmitted/received through anode selected from among a plurality of nodes according to a specificrule. Because a node in a good channel state for a UE is generallyselected, DPS may increase the reliability of signal transmission.

In the present disclosure, a cell refers to a prescribed geographicalarea to which one or more nodes provide a communication service.Accordingly, in the present disclosure, communicating with a specificcell may mean communicating with an eNB or a node which provides acommunication service to the specific cell. In addition, a DL/UL signalof a specific cell refers to a DL/UL signal from/to an eNB or a nodewhich provides a communication service to the specific cell. A nodeproviding UL/DL communication services to a UE is called a serving nodeand a cell to which UL/DL communication services are provided by theserving node is especially called a serving cell. Furthermore, channelstatus/quality of a specific cell refers to channel status/quality of achannel or communication link formed between an eNB or node whichprovides a communication service to the specific cell and a UE. The UEmay measure DL channel state received from a specific node using channelstate information reference signal(s) (CSI-RS(s)) transmitted on aCSI-RS resource, allocated by antenna port(s) of the specific node tothe specific node. In general, adjacent nodes transmit CSI-RSs inmutually orthogonal CSI-RS resources. When it is said that CSI-RSresources are orthogonal, the CSI resources are different in terms of atleast one of a CSI-RS resource configuration which specifies a symboland a subcarrier carrying a CSI-RS, a subframe configuration whichspecifies a subframe to which a CSI-RS is allocated by a subframe offsetand a transmission period, or a CSI-RS sequence.

In the present disclosure, a physical downlink control channel (PDCCH),a physical control format indicator channel (PCFICH), a physical hybridautomatic retransmit request indicator channel (PHICH), and a physicaldownlink shared channel (PDSCH) refer to a set of time-frequencyresources or resource elements (REs) carrying downlink controlinformation (DCI), a set of time-frequency resources or REs carrying acontrol format indicator (CFI), a set of time-frequency resources or REscarrying downlink acknowledgement (ACK)/negative ACK (NACK), and a setof time-frequency resources or REs carrying downlink data, respectively.In addition, a physical uplink control channel (PUCCH), a physicaluplink shared channel (PUSCH) and a physical random access channel(PRACH) refer to a set of time-frequency resources or REs carryinguplink control information (UCI), a set of time-frequency resources orREs carrying uplink data and a set of time-frequency resources or REscarrying random access signals, respectively. In the present disclosure,in particular, a time-frequency resource or RE that is assigned to orbelongs to PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH is referred to asPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH RE orPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH time-frequency resource,respectively. Therefore, in the present disclosure, PUCCH/PUSCH/PRACHtransmission of a UE is conceptually identical to UCI/uplink data/randomaccess signal transmission on PUSCH/PUCCH/PRACH, respectively. Inaddition, PDCCH/PCFICH/PHICH/PDSCH transmission of an eNB isconceptually identical to downlink data/DCI transmission onPDCCH/PCFICH/PHICH/PDSCH, respectively.

FIG. 1 illustrates the structure of a radio frame used in a wirelesscommunication system. Specifically, FIG. 1(a) illustrates an exemplarystructure of a radio frame which can be used in frequency divisionmultiplexing (FDD) in 3GPP LTE/LTE-A and FIG. 1(b) illustrates anexemplary structure of a radio frame which can be used in time divisionmultiplexing (TDD) in 3GPP LTE/LTE-A.

Referring to FIG. 1 , a 3GPP LTE/LTE-A radio frame is 10 ms(307,200T_(s)) in duration. The radio frame is divided into 10 subframesof equal size. Subframe numbers may be assigned to the 10 subframeswithin one radio frame, respectively. Here, T_(s) denotes sampling timewhere T_(s)=1/(2048*15 kHz). Each subframe is 1 ms long and is furtherdivided into two slots. 20 slots are sequentially numbered from 0 to 19in one radio frame. Duration of each slot is 0.5 ms. A time interval inwhich one subframe is transmitted is defined as a transmission timeinterval (TTI). Time resources may be distinguished by a radio framenumber (or radio frame index), a subframe number (or subframe index), aslot number (or slot index), and the like.

A radio frame may have different configurations according to duplexmodes. In FDD mode for example, since DL transmission and ULtransmission are discriminated according to frequency, a radio frame fora specific frequency band operating on a carrier frequency includeseither DL subframes or UL subframes. In TDD mode, since DL transmissionand UL transmission are discriminated according to time, a radio framefor a specific frequency band operating on a carrier frequency includesboth DL subframes and UL subframes.

Table 1 shows an exemplary UL-DL configuration within a radio frame inTDD mode.

TABLE 1 Downlink-to- DL-UL Uplink config- Switch-point Subframe numberuration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U D S U U U 1 5ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D S U U U D DD D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D D D D 6 5 ms D SU U U D S U U D

In Table 1, D denotes a DL subframe, U denotes a UL subframe, and Sdenotes a special subframe. The special subframe includes three fields,i.e. downlink pilot time slot (DwPTS), guard period (GP), and uplinkpilot time slot (UpPTS). DwPTS is a time slot reserved for DLtransmission and UpPTS is a time slot reserved for UL transmission.Table 2 shows an example of the special subframe configuration.

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Special Normal Extended Normal Extended subframecyclic prefix cyclic prefix cyclic prefix cyclic prefix configurationDwPTS in uplink in uplink DwPTS in uplink in uplink 0  6592 · T_(s) 2192· T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 ·T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600· T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592· T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) 12800 · T_(s) 8 24144 · T_(s) — — — 9 13168 ·T_(s) — — —

FIG. 2 illustrates the structure of a DL/UL slot structure in a wirelesscommunication system. Particularly, FIG. 2 illustrates the structure ofa resource grid in the 3GPP LTE/LTE-A system. There is on resource gridper antenna port.

Referring to FIG. 2 , a slot includes a plurality of orthogonalfrequency division multiplexing (OFDM) symbols in the time domain andincludes a plurality of resource blocks (RBs) in the frequency domain.The OFDM symbol may refer to one symbol duration. Referring to FIG. 2 ,a signal transmitted in each slot may be expressed by a resource gridincluding N^(DL/UL) _(RB)*N^(RB) _(sc) subcarriers and N^(DL/DL) _(symb)OFDM symbols. N^(DL) _(RB) denotes the number of RBs in a DL slot andN^(DL) _(RB) denotes the number of RBs in a UL slot. N^(DL) _(RB) andN^(DL) _(RB) depend on a DL transmission bandwidth and a UL transmissionbandwidth, respectively. N^(DL) _(symb) denotes the number of OFDMsymbols in a DL slot, N^(UL) _(symb) denotes the number of OFDM symbolsin a UL slot, and N^(RB) _(sc) denotes the number of subcarriersconfiguring one RB.

An OFDM symbol may be referred to as an OFDM symbol, a single carrierfrequency division multiplexing (SC-FDM) symbol, etc. according tomultiple access schemes. The number of OFDM symbols included in one slotmay be varied according to channel bandwidths and CP lengths. Forexample, in a normal cyclic prefix (CP) case, one slot includes 7 OFDMsymbols. In an extended CP case, one slot includes 6 OFDM symbols.Although one slot of a subframe including 7 OFDM symbols is shown inFIG. 2 for convenience of description, examples of the presentdisclosure are similarly applicable to subframes having a differentnumber of OFDM symbols. Referring to FIG. 2 , each OFDM symbol includesN^(DL/DL) _(RB)*N^(RB) _(sc) subcarriers in the frequency domain. Thetype of the subcarrier may be divided into a data subcarrier for datatransmission, a reference signal (RS) subcarrier for RS transmission,and a null subcarrier for a guard band and a DC component. The nullsubcarrier for the DC component is unused and is mapped to a carrierfrequency f₀ in a process of generating an OFDM signal or in a frequencyup-conversion process. The carrier frequency is also called a centerfrequency f_(c).

One RB is defined as N^(DL/DL) _(symb) (e.g. 7) consecutive OFDM symbolsin the time domain and as N^(RB) _(sc) (e.g. 12) consecutive subcarriersin the frequency domain. For reference, a resource composed of one OFDMsymbol and one subcarrier is referred to a resource element (RE) ortone. Accordingly, one RB includes N^(DL/DL) _(symb)*N^(RB) _(sc) REs.Each RE within a resource grid may be uniquely defined by an index pair(k, l) within one slot. k is an index ranging from 0 to N^(DL/UL)_(RB)*N^(RB) _(sc)−1 in the frequency domain, and l is an index rangingfrom 0 to N^(DL/DL) _(symb)−1 in the time domain.

Two RBs each being located in one of two slots in a subframe, occupyingthe same N^(RB)sc consecutive subcarriers are referred to as a physicalresource block (PRB) pair. The two RBs of a PRB pair have the same PRBnumber (or PRB index). A virtual resource block (VRB) is a kind oflogical resource allocation unit introduced for resource allocation. AVRB is of the same size as a PRB. VRBs are categorized into localizedVRBs and distributed VRBs depending on how VRBs are mapped to PRBs. Thelocalized VRBs are mapped directly to PRBs, and thus VRB numbers (or VRBindexes) correspond directly to PRB numbers. That is, n_(PRB)=n_(VRB).The localized VRBs are indexed as 0 to 1N^(DL) _(VRB)−1, and N^(DL)_(VRB)=N^(DL) _(RB). Accordingly, VRBs of the same VRB number are mappedto PRBs of the same PRB number in the first and second slots in thelocalized mapping scheme. In contrast, distributed VRBs are mapped toPRBs after interleaving. Accordingly, distributed VRBs of the same VRBnumber may be mapped to PRBs of different numbers in the first andsecond slots. Two PRBs of the same VRB number, each being located in oneof two slots in a subframe are referred to as a VRB pair.

FIG. 3 illustrates the structure of a DL subframe used in the 3GPPLTE/LTE-A system.

Referring to FIG. 3 , a DL subframe is divided into a control region anda data region in the time domain. Referring to FIG. 3 , a maximum of 3(or 4) OFDM symbols located in a front part of a first slot of asubframe corresponds to the control region. Hereinafter, a resourceregion for PDCCH transmission in a DL subframe is referred to as a PDCCHregion. OFDM symbols other than the OFDM symbol(s) used in the controlregion correspond to the data region to which a physical downlink sharedchannel (PDSCH) is allocated. Hereinafter, a resource region availablefor PDSCH transmission in the DL subframe is referred to as a PDSCHregion. Examples of a DL control channel used in 3GPP LTE include aphysical control format indicator channel (PCFICH), a physical downlinkcontrol channel (PDCCH), a physical hybrid ARQ indicator channel(PHICH), etc. The PCFICH is transmitted in the first OFDM symbol of asubframe and carries information about the number of OFDM symbolsavailable for transmission of a control channel within a subframe. ThePHICH carries a HARQ (Hybrid Automatic Repeat Request) ACK/NACK(acknowledgment/negative-acknowledgment) signal as a response to ULtransmission.

The control information transmitted through the PDCCH will be referredto as downlink control information (DCI). The DCI includes resourceallocation information for a UE or UE group and other controlinformation. For example, the DCI includes a transmission format andresource allocation information for a downlink shared channel (DL-SCH),a transmission format and resource allocation information for an uplinkshared channel (UL-SCH), paging information of a paging channel (PCH),system information of the DL-SCH, resource allocation information for anupper-layer control message such as a random access response transmittedon a PDSCH, a transmit power control command set for individual UEs of aUE group, a transmit power control command, indication information foractivation of voice over IP (VoIP), a downlink assignment index (DAI),and so on. Transmit format and resource allocation information of adownlink shared channel (DL-SCH) are referred to as DL schedulinginformation or DL grant. Transmit format and resource allocationinformation of an uplink shared channel (UL-SCH) are referred to as ULscheduling information or UL grant. The size and usage of the DCIcarried by one PDCCH are varied depending on DCI formats. The size ofthe DCI may be varied depending on a coding rate. In the current 3GPPLTE system, various formats are defined, wherein formats 0 and 4 aredefined for a UL, and formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 3 and 3Aare defined for a DL. Combination selected from control information suchas a hopping flag, RB allocation, modulation coding scheme (MCS),redundancy version (RV), new data indicator (NDI), transmit powercontrol (TPC), cyclic shift, cyclic shift demodulation reference signal(DM RS), UL index, channel quality information (CQI) request, DLassignment index, HARQ process number, transmitted precoding matrixindicator (TPMI), precoding matrix indicator (PMI) information istransmitted to the UE as the DCI.

Generally, a DCI format, which may be transmitted to the UE, is varieddepending on a transmission mode configured for the UE. In other words,certain DCI format(s) corresponding to the specific transmission modenot all DCI formats may only be used for the UE configured to a specifictransmission mode.

The PDCCH is transmitted on an aggregation of one or a plurality ofcontinuous control channel elements (CCEs). The CCE is a logicallocation unit used to provide a coding rate based on the status of aradio channel to the PDCCH. The CCE corresponds to a plurality ofresource element groups (REGs). For example, one CCE corresponds to 9REGs, and one REG corresponds to four REs. In a 3GPP LTE system, a setof CCEs on which a PDCCH can be located for each UE is defined. A CCEset in which the UE can detect a PDCCH thereof is referred to as a PDCCHsearch space or simply as a search space (SS). An individual resource onwhich the PDCCH can be transmitted in the SS is called a PDCCHcandidate. A set of PDCCH candidates that the UE is to monitor isdefined in terms of SSs. In the 3GPP LTE/LTE-A system, SSs forrespective DCI formats may have different sizes, and a dedicated SS anda common SS are defined. The dedicated SS is a UE-specific SS (USS) andis configured for each individual UE. The common SS (CSS) is configuredfor a plurality of UEs. In a 3GPP LTE/LTE-A system, a set of CCEs onwhich a PDCCH can be located for each UE is defined. A CCE set in whichthe UE can detect a PDCCH thereof is referred to as a PDCCH search spaceor simply as a search space (SS). An individual resource on which thePDCCH can be transmitted in the SS is called a PDCCH candidate. A set ofPDCCH candidates that the UE is to monitor is defined in terms of SSs,where a search space S^((L)) _(k) at aggregation level LE {1, 2, 4, 8}is defined by a set of PDCCH candidates. SSs for respective PDCCHformats may have different sizes and a dedicated SS and a common SS aredefined. The dedicated SS is a UE-specific SS (USS) and is configuredfor each individual UE. The common SS (CSS) is configured for aplurality of UEs.

TABLE 3 Search Space S_(K) ^((L)) Number of Aggregation PDCCH Type LevelL Size[in CCEs] candidates M^((L)) UE-specific 1 6 6 2 12 6 4 8 2 8 16 2Common 4 16 4 8 16 2

One PDCCH candidate corresponds to 1, 2, 4, or 8 CCEs according to a CCEaggregation level. An eNB transmits an actual PDCCH (DCI) on a PDCCHcandidate in a search space and the UE monitors the search space todetect the PDCCH (DCI). Here, monitoring implies attempting to decodeeach PDCCH in the corresponding SS according to all monitored DCIformats. The UE may detect a PDCCH thereof by monitoring a plurality ofPDCCHs. Basically, the UE does not know the location at which a PDCCHthereof is transmitted. Therefore, the UE attempts to decode all PDCCHsof the corresponding DCI format for each subframe until a PDCCH havingan ID thereof is detected and this process is referred to as blinddetection (or blind decoding (BD)).

The eNB may transmit data to a UE or UE group in a data region. Datatransmitted in the data region is referred to as user data. Fortransmission of user data, a physical downlink shared channel (PDSCH)may be allocated in the data region. A paging channel (PCH) and a DL-SCHare transmitted on the PDSCH. A UE may read data transmitted on a PDSCHby decoding control information transmitted on a PDCCH. Informationregarding a UE or UE group to which data of the PDSCH is transmitted,and information regarding how the UE or UE group should receive anddecode the PDSCH data may be transmitted on the PDCCH. For example, itis assumed that a specific PDCCH is CRC-masked with a radio networktemporary identity (RNTI) ‘A’ and information about data transmittedusing a radio resource ‘B’ (e.g. frequency location) and using transportformat information ‘C’ (e.g. transmission block size, modulation scheme,coding information, etc.) is transmitted in a specific DL subframe.Then, the UE monitors the PDCCH using RNTI information thereof. The UEhaving the RNTI ‘A’ receives the PDCCH and receives the PDSCH indicatedby ‘B’ and ‘C’ through information of the received PDCCH.

To demodulate a signal received from the eNB, the UE needs a referencesignal (RS) to be compared with a data signal. An RS is a signal in apredefined special waveform, which the eNB or the UE transmits to the UEor the eNB or which is known to both of the eNB and the UE. The RS isalso called a pilot. RSs are classified into cell-specific RS (CRS)common to all UEs within a cell and demodulated RS (DM RS) dedicated toa specific UE. A DM RS that the eNB transmits for demodulation of DLdata at a specific UE is specially called a UE-specific RS. Only one orboth of the DM RS and the CRS may be transmitted on DL. However, whenonly the DM RS without the CRS is transmitted on the DL, the DM RS towhich the same precoder as that for data is applied may be used only fordemodulation. Therefore, an RS for channel measurement should beprovided separately. For example, an additional measurement RS, CSI-RSis transmitted to the UE to enable the UE to measure channel stateinformation (CSI) in 3GPP LTE(-A). Compared to the CRS transmitted ineach subframe, the CSI-RS is transmitted in every predeterminedtransmission period including a plurality of subframes, based on theproperty that a channel state does not change relatively much over time.

FIG. 4 illustrates the structure of a UL subframe used in the 3GPPLTE/LTE-A system.

Referring to FIG. 4 , a UL subframe may be divided into a data regionand a control region in the frequency domain. One or several PUCCHs maybe allocated to the control region to deliver UCI. One or several PUSCHsmay be allocated to the data region of the UE subframe to carry userdata.

In the UL subframe, subcarriers distant from a direct current (DC)subcarrier are used as the control region. In other words, subcarrierslocated at both ends of a UL transmission BW are allocated to transmitUCI. A DC subcarrier is a component unused for signal transmission andis mapped to a carrier frequency f₀ in a frequency up-conversionprocess. A PUCCH for one UE is allocated to an RB pair belonging toresources operating on one carrier frequency and RBs belonging to the RBpair occupy different subcarriers in two slots. The PUCCH allocated inthis way is expressed by frequency hopping of the RB pair allocated tothe PUCCH over a slot boundary. If frequency hopping is not applied, theRB pair occupies the same subcarriers.

The PUCCH may be used to transmit the following control information.

-   -   Scheduling request (SR): SR is information used to request a        UL-SCH resource and is transmitted using an on-off keying (OOK)        scheme.    -   HARQ-ACK: HARQ-ACK is a response to a PDCCH and/or a response to        a DL data packet (e.g. a codeword) on a PDSCH. HARQ-ACK        indicates whether the PDCCH or PDSCH has been successfully        received. 1-bit HARQ-ACK is transmitted in response to a single        DL codeword and 2-bit HARQ-ACK is transmitted in response to two        DL codewords. A HARQ-ACK response includes a positive ACK        (simply, ACK), negative ACK (NACK), discontinuous transmission        (DTX), or NACK/DRX. HARQ-ACK is used interchangeably with HARQ        ACK/NACK and ACK/NACK.    -   Channel state information (CSI): CSI is feedback information for        a DL channel. In the CSI, multiple input multiple output (MIMO)        related feedback information includes the rank indicator (RI)        and the precoding matrix indicator (PMI).

The amount of uplink control information (UCI) that the UE may transmitin a subframe depends on the number of SC-FDMA symbols available fortransmission of control information. The SC-FDMA symbols available forthe UCI refer to the remaining SC-FDMA symbols except for SC-FDMAsymbols used for RS transmission in an SC-FDMA subframe, and also exceptfor the last SC-FDMA symbol in a subframe with a sounding referencesignal (SRS). The RS is used for coherent detection of a PUCCH. ThePUCCH supports various formats according to the amount of transmittedinformation.

Table 4 illustrates mapping relationships between PUCCH formats and UCIin the LTE/LTE-A system.

TABLE 4 Number of PUCCH Modulation bits per format scheme subframe UsageEtc. 1 N/A N/A (exist SR (Scheduling or absent) Request) 1a BPSK 1ACK/NACK or One codeword SR + ACK/NACK 1b QPSK 2 ACK/NACK or Twocodeword SR + ACK/NACK 2 QPSK 20 CQI/PMI/RI Joint coding ACK/NACK(extended CP) 2a QPSK + BPSK 21 CQI/PMI/RI + Normal ACK/NACK CP only 2bQPSK + QPSK 22 CQI/PMI/RI + Normal ACK/NACK CP only 3 QPSK 48 ACK/NACKor SR + ACK/NACK or CQI/PMI/RI + ACK/NACK

Referring to Table 4, the PUCCH format 1 series are mainly used todeliver ACK/NACK information, the PUCCH format 2 series are mainly usedto deliver channel state information (CSI) such as CQI/PMI/RI, and thePUCCH format 3 series are mainly used to deliver ACK/NACK information.

Reference Signal (RS)

When a packet is transmitted in a wireless communication system, thesignal may be distorted during transmission because the packet istransmitted on a radio channel. To correctly receive the distortedsignal, a receiver should compensate the received signal for thedistortion based on channel information. Typically, a signal known toboth the transmitter and the receiver is transmitted, and the channelinformation is obtained based on how much the signal is distorted duringreception on the radio channel. This signal is called a pilot signal ora reference signal (RS).

When data is transmitted and received through multiple antennas,knowledge of the channel state between each transmission antenna andeach reception antenna is required to receive a correct signal.Therefore, an RS should exist for each individual transmission antennaand more specifically for each individual antenna port.

RSs may be classified into UL RSs and DL RSs. In the current LTE system,the following UL RSs are defined.

i) Demodulation reference signal (DM-RS) for channel estimation forcoherent demodulation of information transmitted over a PUSCH and aPUCCH

ii) Sounding reference signal (SRS) in which an eNB measures UL channelquality in different frequencies.

The following DL RSs are defined.

i) Cell-specific reference signal (CRS) shared by all UEs within a cell.

ii) UE-specific reference signal dedicated to a specific UE.

iii) DM-RS transmitted for coherent demodulation, when a PDSCH istransmitted.

iv) Channel state information reference signal (CSI-RS) for deliveringCSI, when DL DMRS is transmitted.

v) Multimedia broadcast single frequency network (MBSFN) RS transmittedfor coherent demodulation of a signal transmitted in an MBSFN mode.

vi) Positioning reference signal used to estimate information about thegeographical location of a UE.

RSs may be classified into two types according to their purposes: RS forobtaining channel information and RS for data demodulation. Because theformer is used for a UE to acquire DL channel information, it should betransmitted over a wide band and received even at a UE which does notreceive DL data in a specific subframe. The former is also used in asituation such as handover. The latter is an RS that an eNB transmitstogether with DL data in a corresponding resource, and a UE maydemodulate data by receiving the RS and performing channel measurement.This RS should be transmitted in an area in which data is transmitted.

Carrier Aggregation (CA)

CA is a technique of using a plurality of frequency blocks or (logical)cells including UL resources (or component carriers (CCs) and/or DLresources (or CCs) as one large logical frequency band by a UE, so thata wireless communication system may use a wider frequency band.

One DL CC and one UL CC are used in the LTE system, whereas multiple CCsmay be used in the LTE-A system. Two methods are available forscheduling a data channel by a control channel: link/self-carrierscheduling and cross-carrier scheduling (CCS).

More specifically, in the link/self-carrier scheduling, a controlchannel transmitted in a specific CC schedules only a data channel inthe specific CC as in the legacy LTE system using a single CC.

On the other hand, in the cross-carrier scheduling, a control channeltransmitted in a primary CC schedules a data channel transmitted in theprimary CC or another CC by using a carrier indicator field (CIF).

Enhanced PDCCH (EPDCCH) Overview

Although the introduction of a multi-node system enables application ofvarious communication schemes, and thus channel quality may be improved,the introduction of a new control channel is required to apply MIMO andCoMP as described before to a multi-node environment. In this context,enhanced PDCCH (EPDCCH) has been introduced to the LTE-A system. TheEPDCCH is allocated in a data region, not in a control region of atransmission time interval (TTI) or a subframe. Consequently, the EPDCCHenables transmission of control information about a node to each UE,thereby overcoming the conventional problem of an insufficient PDCCHregion.

In order to satisfy requirements for various application fields, it maybe considered to configure various transmission time intervals (TTIs)(or various TTI lengths) for all or a specific physical channel in thenext-generation system. More characteristically, a TTI during which aphysical channel such as a PDCCH/PDSCH/PUSCH/PUCCH is transmitted may beset to be less than 1 msec to reduce latency for communication betweenan eNB and a UE according to a scenario (such a PDCCH/PDSCH/PUSCH/PUCCHis referred to as an sPDCCH/sPDSCH/sPUSCH/sPUCCH). For a single UE ormultiple UEs, a plurality of physical channels may exist in a singlesubframe (e.g., 1 msec), and have different TTIs (or TTI lengths). Thefollowing examples will be described in the context of an LTE system,for the convenience of description. A TTI may be 1 msec (normal TTI),the length of a normal subframe used in the LTE system, and a short TTIis a TTI shorter than the normal TTI, spanning one or more OFDM orSC-FDMA symbols. While a short TTI (i.e., a TTI shorter than a legacyone subframe) is taken for the convenience of description, the keyfeatures of the present disclosure may be extended to a TTI longer thanone subframe or equal to or longer than 1 ms. Characteristically, thekey features of the present disclosure may also be extended to a shortTTI which is introduced to the next-generation system by increasing asubcarrier spacing. Although the present disclosure is described in thecontext of LTE, for convenience, it is applicable to a technology usinga different waveform/frame structure such as new radio access technology(RAT). In general, the present disclosure is based on the assumption ofan sTTI (<1 msec), a longTTI (=1 msec), and a longerTTI (>1 msec). Whilea plurality of UL channels having different TTIlengths/numerologies/processing times have been described above, it isapparent that the following examples may be extended to a plurality ofUL/DL channels to which different service requirements, latencies, andscheduling units are applied.

To fulfill the above-described latency reduction, that is, low latency,there is a need for designing a new shortened TTI (sTTI) of 0.5 msec orless by shortening the minimum data transmission unit, TTI. For example,to reduce the user plane (U-plane) latency from the beginning of data(PDCCH and PDSCH) transmission from an eNB to complete transmission ofan A/N (or ACK/NACK) from a UE to 1 msec as illustrated in FIG. 5 , ansTTI may be configured in units of 3 OFDM symbols.

In a DL environment, a PDCCH (i.e., sPDCCH) designed fortransmission/scheduling of data in an sTTI, and a PDSCH (i.e., sPDSCH)designed to be transmitted in an sTTI may be transmitted in such ansTTI. For example, as illustrated in FIG. 6 , a plurality of sTTIs maybe configured with different OFDM symbols in one subframe.Characteristically, OFDM symbols included in the sTTI may be configuredto exclude OFDM symbols carrying legacy control channels. In the sTTI,an sPDCCH and an sPDSCH may be transmitted in time division multiplexing(TDM) in different OFDM symbol regions, or in frequency divisionmultiplexing (FDM) in different PRB regions/frequency resources.

Like the above-described DL environment, data may betransmitted/scheduled in a sTTI in a UL environment, and channelscorresponding to the existing TTI-based PUCCH and PUSCH are referred toas sPUCCH and sPUSCH.

The present disclosure is described in the context of the LTE/LTE-Asystem. In the legacy LTE/LTE-A system, a 1-ms subframe includes 14 OFDMsymbols in the case of a normal CP. When a TTI is configured to beshorter than 1 ms, a plurality of TTIs may be included in one subframe.In a method of configuring a plurality of TTIs, two symbols, threesymbols, four symbols, and seven symbols may be configured as one TTI,as illustrated in FIG. 7 . Although not shown, a TTI spanning one symbolmay also be considered. If one symbol is one TTI unit, 12 TTIs areformed on the assumption that the legacy PDCCH is transmitted in twoOFDM symbols. Similarly, as illustrated in FIG. 7A, when two symbols areone TTI unit, six TTIs may be formed. When three symbols are one TTIunit, four TTIs may be formed as illustrated in FIG. 7B. When foursymbols are one TTI unit, three TTIs may be formed as illustrated inFIG. 7(c). In this case, it is assumed that the legacy PDCCH istransmitted in the first two OFDM symbols.

As illustrated in FIG. 7(d), when seven symbols are configured as oneTTI, one TTI of seven symbols carrying the legacy PDCCH and one TTI ofthe next seven symbols may be configured. If one TTI is configured withseven symbols, a UE supporting sTTI may assume that the first two OFDMsymbols carrying the legacy PDCCH have been punctured or rate-matchedand the following five symbols carry data and/or control information forthe UE in the TTI (first slot) located at the former part of onesubframe. For the TTI (second slot) located in the latter part of thesubframe, the UE assumes that data and/or control information may betransmitted in all of the seven symbols without any puncturing orrate-matching resource regions.

In the present disclosure, an sTTI structure in which an sTTI spanningtwo OFDM symbols (hereinafter, referred to as “OSs”) coexists with ansTTI spanning three OSs as illustrated in FIG. 8 is also considered. A2-OS or 3-OS sTTI may be simply defined as a 2-symbol sTTI (i.e., a 2-OSsTTI). Further, a 2-symbol sTTI or 3-symbol sTTI may be referred tosimply as a 2-symbol TTI or 3-symbol TTI. All of these sTTIs are shorterthan the legacy 1-ms TTI according to the present disclosure. That is,despite the term “TTI”, it does not mean that the TTI is not an sTTI,and the present disclosure relates to a communication scheme in a systemconfigured with a TTI shorter than the legacy TTI, irrespective of theappellation.

Further, in the present disclosure, a numerology refers to determiningthe length of a TTI, a subcarrier spacing, and so on to be applied tothe wireless communication system, a parameter such as a determined TTIlength or subcarrier spacing, or a communication structure or systembased on the parameter.

In the <3, 2, 2, 2, 2, 3> sTTI pattern illustrated in FIG. 8(a), ansPDCCH may also be transmitted according to the number of symbols in aPDCCH. In the <2, 3, 2, 2, 2, 3> sTTI pattern illustrated in FIG. 8(b),transmission of an sPDCCH may be difficult because of the legacy PDCCHregion.

New Radio Technology (NR)

While the structure, operation, or function of the 3GPP LTE(-A) systemhas been described above, the structure, operation, or function of the3GPP LTE(-A) system may be slightly modified or implemented in otherways in NR. Some of the modifications and implementations will bebriefly described.

In NR, various numerologies are supported. For example, a subcarrierspacing of up to a 2^(n) multiple of 15 KHz (n=1, 2, 3, 4) as well as asubcarrier spacing of 15 KHz is supported.

Further, in the case of a normal CP, although the number of OFDM symbols(hereinafter, simply referred to as “symbols”) per slot is fixed to 14,the supported number of slots in one subframe is up to 2^(k) (k=0, 1, 2,3, 4, and 5) and a radio frame includes 10 subframes as in the legacyLTE system. In the case of an extended CP, the number of symbols perslot is fixed to 12, and one subframe includes 4 slots. Further, oneresource block (RB) is defined as 12 consecutive subcarriers in thefrequency domain, as in the legacy LTE system.

Further, the use (e.g., DL, UL, or flexible) of each symbol in one slotmay be defined according to a slot format, and both a DL symbol and a ULsymbol may be configured in one slot. This case is referred to as aself-contained subframe (or slot) structure.

Multi-TTI Scheduling

As a method of reducing latency, it is considered to define and transmita shorter TTI. For example, it is considered to define a PDSCH and aPUSCH having a 2-symbol or 3-symbol sTTI and transmit/receive DL data onthe PDSCH and UL data on the PUSCH. However, this method may increasecontrol overhead because a control channel for scheduling should also betransmitted in each TTI. As one solution to this problem, multi-TTIscheduling may be considered, in which one control channel schedules aplurality of TTIs. When multi-TTI scheduling is considered, thefollowing is proposed.

HARQ-ACK Resources for Multi-TTI Scheduling

It may be regulated that HARQ-ACK resources for PDSCHs scheduled bymulti-TTI scheduling DCI are determined as follows.

Alt 1: A HARQ-ACK resource for a specific one of a plurality ofscheduled TTIs may be indicated by multi-TTI scheduling DCI, andHARQ-ACK resources for the remaining scheduled TTIs may be implicitlydetermined. For example, HARQ-ACK resource for the first of theplurality of scheduled TTIs may be determined by the lowest CCE index ofthe multi-TTI scheduling DCI or according to specific resourcesassociated with a specific state of an A/N resource indicator (ARI), andHARQ-ACK resources for the remaining scheduled TTIs may be determined tobe resources to which an offset from the determined resources isapplied.

Here, the offset (or a set of offsets to be applied to the plurality ofrespective TTIs) may be 0, and may be a pre-configured value accordingto the indexes of the scheduled TTIs and/or information about which onesare the scheduled TTIs. Alternatively, the offset (or the set of offsetsto be applied to the plurality of respective TTIs) may beindicated/configured by DCI or higher-layer signaling. In a morespecific example, it may be regulated that, when the index of a PUCCHresource for the first scheduled TTI is m, the indexes of PUCCHresources for the second and third scheduled TTIs are determined to bem+1 and m+2, respectively.

Alt 2: HARQ-ACK resource information for a plurality of TTIs may bepre-configured for the respective states of an ARI, and PUCCHresource(s) for scheduled TTI(s) may be determined by a specific stateof the ARI indicated in multi-TTI scheduling DCI. For example, for eachstate of the ARI, PUCCH resources corresponding to a maximum number ofTTIs that may be scheduled by multi-TTI scheduling are configured. Itmay be regulated that, when multi-TTI scheduling DCI schedules fewerTTIs than the number, as many PUCCH resources as the number of scheduledTTIs are used among the PUCCH resources corresponding to the indicatedstate of the ARI.

PDCCH Blind Decoding (BD) in Case of Multi-TTI Scheduling

It may be regulated that a PDCCH RB set for monitoring multi-TTIscheduling DCI is separately configured. Alternatively, it may beregulated that an aggregation level (AL) and/or the number of BDcandidates (or a reduction factor of BD candidates) for monitoringmulti-TTI scheduling DCI is independently configured for each PDCCH RBset. Characteristically, this may be distinguished from that formonitoring single-TTI scheduling DCI. Alternatively, among parameters ina PDCCH RB set, it may be indicated whether multi-TTI scheduling isenabled by higher-layer signaling.

Use of Unused Resources

To reduce control overhead, use of resources other than those used forcontrol channels for data channel transmission may be allowed to therebymaximize the utilization of unused resources. To this end, variousschemes are being considered, and when multi-TTI scheduling is applied,it may also be desirable to configure maximum utilization of unusedresources.

Characteristically, it may be regulated that among a plurality of TTIsscheduled by multi-TTI scheduling DCI, rate-matching of data is allowedin an RB or RBG indicated by a specific (or every) PDCCH RB set in a TTIthat does not include the DCI. Regarding the above configuration, oneconfiguration may be commonly applied to a plurality of TTIs to whichmulti-TTI scheduling has been applied, and a different configuration maybe applied to each of the plurality of TTIs. This may be useful whenmulti-TTI scheduling has been performed and scheduling pre-emption isnot allowed for a plurality of scheduled TTIs.

Signaling of TTI which is not Multi-TTI-Scheduled

Multi-TTI scheduling DCI may indicate whether some or all of a pluralityof TTIs in a specific period have been scheduled, and it may beregulated that a UE does not monitor a TTI indicated as not scheduled.Alternatively, it may be regulated that when TTIs scheduled by multi-TTIscheduling DCI are indicated by higher-layer signaling, a UE does notmonitor DCI in a TTI that does not include the multi-TTI scheduling DCIamong the plurality of scheduled TTIs.

Configuration of TTI for Transmission of CSI Report or SRS AmongMultiple TTIs

When multi-TTI scheduling is applied based on the proposed method or anyother method, it may be necessary to configure a TTI time pointcorresponding to a CSI request and an SRS request in multi-TTIscheduling DCI (e.g., a transmission time of a PUSCH including anaperiodic CSI feedback). Characteristically, the TTI time point may beconfigured to be the first or last TTI including a DMRS among aplurality of scheduled TTIs, a pre-configured TTI, or a TTI indicated byDCI. This may allow CSI reporting only when the DMRS exists in thecorresponding TTI, for reliable transmission of the triggered CSI.

Alternatively, the TTI time point may be configured to be the first orlast TTI without a DMRS among a plurality of scheduled TTIs, apre-configured TTI, or a TTI indicated by DCI. Because rate matchingcaused by CSI may increase the coding rate of a PUSCH transmission, aCSI report may be included in a TTI without a DMRS to reduce the codingrate increase.

In another method, it may be regulated that a CSI report is repeatedlyincluded in some (or all) of a plurality of scheduled TTIs. This mayfurther increase the reliability of CSI.

SRS Transmission TTI

When multi-TTI scheduling is applied based on the proposed method or anyother method, it may be necessary to configure a TTI time pointcorresponding to an SRS request in multi-TTI scheduling DCI (e.g., atransmission time of an aperiodic SRS), and an SRS may be transmitted inthe last TTI belonging to an SRS subframe among a plurality of scheduledTTIs. Alternatively, an SRS transmission TTI (e.g., an SRS sTTI) may bedefined separately, and if there is an SRS transmission TTI among aplurality of scheduled TTIs, an SRS may be transmitted in the SRStransmission TTI.

HARQ-ACK Transmission TTI

When multi-sTTI scheduling is performed, an HARQ-ACK may be transmittedat an HARQ-ACK timing corresponding to each sPDSCH, and alternatively anaggregated and/or bundled HARQ-ACK for multi-sTTI sPDSCHs may betransmitted. Alternatively, one of the two methods may be configured bythe network. In the former case, PUCCH/UCI overhead may increase despitefast HARQ-ACK response, whereas in the latter case, latency mayincrease. Further, when one TB is mapped to multi-sTTI scheduling, itmay be assumed that the timing of an HARQ-ACK is configured based on thelast sTTI, and that the HARQ-ACK is transmitted in a correspondingPUCCH/UCI resource at the timing. Further, an HARQ-ACK scheme may beassociated with a retransmission. Even though multi-sTTI scheduling isperformed, only some of TBs may be retransmitted by single-sTTIscheduling. Even for a retransmission, multi-sTTI scheduling may beused, but a subset of initially transmitted TBs may be transmitted atthe retransmission. That is, it may be assumed that only a TBcorresponding to NACK or DTX is transmitted at a retransmission. If aretransmission is scheduled in a single sTTI, or if single-sTTI DCI andmulti-sTTI DCI may coexist, it may be assumed that a DCI size isadjusted using padding or the like, and an indication regarding a singlesTTI or multiple sTTIs may be added to corresponding DCI. Alternatively,a DCI size may be configured for each PRB set to separately transmitmultiple sTTIs and a single sTTI.

Cross-Carrier Scheduling

When it is possible to configure an independent (different) processingtime for each cell, there may be a need for a rule between an eNB and aUE, for deriving a processing time in the case of cross-carrierscheduling. For example, when processing time configurations of ascheduling cell and a scheduled cell indicate different processingtimes, the UE may face ambiguity in determining which processing time isto be taken to determine a DL allocation-to-DL data processing timeand/or a DL data-to-DL HARQ processing time and/or a UL grant-to-UL dataprocessing time. Accordingly, it may be regulated that only when theprocessing time configurations of a scheduling cell and a scheduled cellindicate the same processing time, cross-carrier scheduling is allowed.

Cross-carrier scheduling is defined as follows in the current LTEstandard (TS 36.331).

CrossCarrierSchedulingConfig

The IE CrossCarrierSchedulingConfig is used to specify the configurationwhen the cross carrier scheduling is used in a cell.

CrossCarrierSchedulingConfig information elements

ASN1START CrossCarrierSchedulingConfig-r10 ::=   SEQUENCE {schedulingCellInfo-r10         CHOICE { own-r10                    SEQUENCE {      -- No cross carrier schedulingcif-Presence-r10               BOOLEAN }, other-r10                     SEQUENCE {      -- Cross carrier scheduling schedulingCellId-r10         ServCellIndex-r10, pdsch-Start-r10                INTEGER (1 .. . 4) } } } ASN1STOP

TABLE 5 CrossCarrierSchedulingConfig field descriptions cif-Presence Thefield is used to indicate whether carrier indicator field is present(value TRUE) or not (value FALSE) in PDCCH/EPDCCH DCI formats, see TS36.212 [22, 5.3.3.1] pdsch-Start The starting OFDM symbol of PDSCH forthe concerned SCell, see TS 36.213 [23.7.1.6.4] Values 1, 2, 3 areapplicable when dl-Bandwidth for the concerned SCell is greater than 10resource blocks, values 2, 3, 4 are applicable when dl-Bandwidth for theconcerned SCell is less than or equal to 10 resource blocks, see TS36.211 [21, Table 6, 7-1]. schedulingCellId Indicates which cell signalsthe downlink allocations and uplink grants, if applicable, for theconcerned SCell. In case the UE is configured with DC, the schedulingcell is part of the same cell group (i.e. MCG or SCG) as the scheduledcell.

The above cross-carrier scheduling-related configuration (e.g.,scheduling cell information, PDSCH starting symbol information, and soon) may be configured for or applied to the UE regardless of aprocessing time-related configuration. In this case, a scheduling celland a scheduled cell may have different processing times, and a relatedUE operation needs to be defined. In this case, for example, the UE maytake the longer between the two processing times as its DLallocation-to-DL data and/or DL data-to-DL HARQ and/or UL grant-to-ULdata processing time in order to secure a conservative processing timemargin.

Alternatively, the cross-carrier scheduling-related configuration may beinterpreted differently by the processing time-related configuration ofthe scheduled cell. For example, even though cross-carrier scheduling isconfigured for a specific scheduled cell, when the processing time ofthe scheduled cell is configured to be different from the processingtime of a cell that schedules the corresponding cell (e.g., theprocessing time of the scheduled cell is n+3, and the processing time ofthe scheduling cell is n+4), only self-carrier scheduling, notcross-carrier scheduling is applied to the scheduled cell. Accordingly,it may be regulated that the UE monitors DL assignment/UL grant DCI forthe scheduled cell in a search space configured in the scheduled cell.

Alternatively, when a short processing time is configured for a specificcell, a cross-carrier scheduling-related configuration may also beconfigured separately. Characteristically, even though cross-carrierscheduling of a specific cell is originally enabled, the cross-carrierscheduling may be disabled along with the configuration of the shortprocessing time. Alternatively, a scheduling cell and/or a PDSCHstarting symbol indicated by a cross-carrier scheduling-relatedconfiguration of the specific cell, and a scheduling cell and/or a PDSCHstarting symbol configured by the configuration of a short processingtime may be indicated to be different.

If cross-carrier scheduling by serving cell Y is configured for a datachannel to be transmitted in serving cell X and sTTI is configured forserving cell X, the UE may monitor a PDCCH/EPDCCH of serving cell Y fora data channel of a subframe duration to be transmitted in serving cellX, and monitor a PDCCH/SPDCCH of serving cell X for a data channel of aslot/subslot duration to be transmitted in serving cell X.

As such, monitoring control channels in a plurality of serving cells,for data channels having different durations to be transmitted in onecell, may not be preferable because it may affect the processing time ofthe UE. Therefore, the following operations are proposed for a UEreceiving the above configuration.

Option 1: In order to reduce the effect on the processing time of theUE, it may be regulated that only self-carrier scheduling is supportedregardless of the duration of a data channel. In other words, the UEmonitors, only in serving cell X, control channels that schedule datachannels to be transmitted in serving cell X. This may be interpreted asthe UE ignoring a cross-carrier scheduling configuration.Characteristically, for a data channel to be transmitted in serving cellX, the UE may monitor only a PDCCH and/or SPDCCH, except for an EPDCCH,in serving cell X.

Option 2: It may be regulated that a UE capability is reported,regarding whether the UE supports monitoring of control channels in aplurality of serving cells, for data channels having different durationsto be transmitted in one cell. That is, the UE may report its capabilityas to whether the UE supports simultaneous monitoring of a PDCCH/EPDCCHthat schedules a subframe-PDSCH/PUSCH in cell Y and a PDCCH/SPDCCH thatschedules a slot/subslot-PDSCH/PUSCH in cell X. It may be regulatedthat, if the UE reports that the operation is supported, thesubframe-PDSCH/PUSCH is scheduled by cross-carrier scheduling and theslot/subslot-PDSCH/PUSCH is scheduled by self-carrier scheduling, andthe UE monitors each control channel in a corresponding cell. It may beregulated that, if the operation is reported as unsupportable, all datachannels having different durations are operated by self-carrierscheduling as in option 1 and accordingly, the UE monitors the controlchannels in the corresponding cells.

The monitoring operation may be applied to an operation of monitoring aplurality of control channels, for data channels having differentdurations, even though time periods in which the plurality of controlchannels are actually monitored, for the data channels having differentdurations, do not overlap with each other.

Option 3: For data channels having different durations to be transmittedin one cell (herein, a duration includes a TTI length), the UE does notexpect that cross-carrier scheduling is configured for a data channelhaving any one duration. In other words, it may be regulated that onlyself-carrier scheduling is configured for data channels of alldurations/TTI lengths/numerologies/target BLERs configured (orsupported) in a specific cell. The specific cell may include a cell forwhich a different duration/TTI length/numerology/target BLER isconfigured or pre-configured. This configuration may be appliedregardless of the capability of simultaneously receiving a plurality ofdata channels having different durations.

Option 4: In another method, as regards data channels having differentdurations to be transmitted in one cell (herein, a duration includes aTTI length), it may be regulated that, for a data channel of a specificduration (e.g., a subframe-PDSCH) of a specific cell, self-carrierscheduling, or cross-carrier scheduling from a cell for which no EPDCCHis configured, is configured. That is, it may be regulated that for adata channel of a specific duration (e.g., a subframe-PDSCH) of aspecific cell, the UE monitors a control channel in the cell, ormonitors only a control channel (e.g., a PDCCH) other than an EPDCCHwhen cross-carrier scheduling is performed in another cell. The specificcell may be a cell for which a different duration/TTIlength/numerology/target BLER is configured or pre-configured. Thisconfiguration may be applied regardless of the capability ofsimultaneously receiving multiple data channels with differentdurations/TTI lengths/numerologies/target BLERs.

The monitoring operation may be applied to an operation of monitoring aplurality of control channels for data channels having differentdurations, even though time periods in which the plurality of controlchannels are actually monitored for the data channels having differentdurations/TTI lengths/numerologies/target BLERs do not overlap with eachother.

Dynamic Fallback to Transmit Diversity

An sTTI operation is an operation configured to reduce latency accordingto a UE capability that a UE has reported to the network in an RRCConnected mode. In order to prevent an excessive increase in the BDs ofan (S)PDCCH at the UE, a DCI format for fallback transmission is notseparately defined in the sTTI operation. It may be regulated that, ifthe eNB wants to perform fallback to a transmission scheme such astransmit diversity due to a change in a channel state, the fallback isindicated to the UE by using (reusing) a specific field in a DCI formatthat the UE monitors according to a transmission mode (TM) defined andconfigured by TM-dependent DCI. Thus, the UE may dynamically fall backfrom a transmission scheme based on the configured TM to the transmitdiversity transmission scheme to expect a higher reception rate for a DLdata channel. In the sTTI operation, if dynamic fallback is notsupported, the eNB should always perform scheduling by using thelegacy/default TTI (e.g., a 1-ms TTI) when it wants to fall back to atransmission scheme such as transmit diversity, which may cause a highDL latency.

It may be regulated that for the sTTI operation, a UE reports a UEcapability as to whether the UE supports dynamic fallback to a specifictransmission scheme (e.g., transmit diversity) to the network bysignaling. Characteristically, the UE capability signaling may beindependently defined for each TTI length (or each TTI group including aplurality of TTI lengths). This is because whether the UE supportsdynamic fallback to the transmit diversity transmission scheme may bedifferent for each TTI length. Further, a configuration of the eNB orthe network that performs dynamic fallback to a specific transmissionscheme (e.g., transmit diversity) may be independently configured foreach TTI length (or a TTI length group including a plurality of TTIlengths) by higher-layer signaling.

Additionally or alternatively, the UE capability signaling may includeinformation about the number of supported antenna ports. For example, itmay be reported that only 2-port transmit diversity is supported, orboth 2-port transmit diversity and 4-port transmit diversity aresupported. Further, the configuration of the eNB or network thatperforms dynamic fallback to a specific transmission scheme (e.g.,transmit diversity) may include information about the number of antennaports and may be configured by higher-layer signaling.

The UE capability signaling may be independently defined for each TM (oreach TM group including a plurality of TMs) configured for the sTTIoperation. Whether or not dynamic fallback is support may be differentin each TM configured for the UE, and the eNB may determine whether toperform the dynamic fallback in an sTTI based on the UE capabilitysignaling. Further, a DCI field for dynamic fallback may also beinterpreted differently based on the UE capability signaling (and/or theconfiguration of the eNB or network to enable/disable dynamic fallback).Alternatively, regardless of a TM configured for the sTTI operation,common UE capability signaling may be defined, which may be interpretedas always supporting fallback to the transmit diversity transmissionscheme, if the UE supports the sTTI operation. The eNB may also becapable of performing transmit diversity irrespective of a configuredTM, thereby avoiding unnecessary latency. Further, the configuration ofthe eNB or the network that performs dynamic fallback to a specifictransmission scheme (e.g., transmit diversity) may be configuredirrespective of a TM configured for a sTTI or independently for each TM(group) configured for the sTTI by higher-layer signaling.

Since examples of the above proposed methods may be included as one ofmethods of implementing the present disclosure, it is apparent that theexamples may be regarded as proposed methods. Further, the foregoingproposed methods may be implemented independently, or some of themethods may be implemented in combination (or merged). Further, it maybe regulated that information indicating whether the proposed methodsare applied (or information about the rules of the proposed methods) isindicated to a UE by a pre-defined signal (or a physical-layer orhigher-layer signal) by an eNB.

FIG. 9 is a block diagram illustrating elements of a transmitting device10 and a receiving device 20 for implementing the present disclosure.The transmitting device 10 and the receiving device 20 respectivelyinclude transceivers 13 and 23 capable of transmitting and receivingradio signals carrying information, data, signals, and/or messages,memories 12 and 22 for storing information related to communication in awireless communication system, and processors 11 and 21 operationallyconnected to elements such as the transceivers 13 and 23 and thememories 12 and 22 to control the elements and configured to control thememories 12 and 22 and/or the transceivers 13 and 23 so that acorresponding device may perform at least one of the above-describedexamples of the present disclosure.

The memories 12 and 22 may store programs for processing and controllingthe processors 11 and 21 and may temporarily store input/outputinformation. The memories 12 and 22 may be used as buffers. Theprocessors 11 and 21 generally control the overall operation of variousmodules in the transmitting device and the receiving device. Especially,the processors 11 and 21 may perform various control functions toimplement the present disclosure. The processors 11 and 21 may bereferred to as controllers, microcontrollers, microprocessors, ormicrocomputers. The processors 11 and 21 may be implemented by hardware,firmware, software, or a combination thereof. In a hardwareconfiguration, application specific integrated circuits (ASICs), digitalsignal processors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), or field programmable gate arrays(FPGAs) may be included in the processors 11 and 21. Meanwhile, if thepresent disclosure is implemented using firmware or software, thefirmware or software may be configured to include modules, procedures,functions, etc. performing the functions or operations of the presentdisclosure. Firmware or software configured to perform the presentdisclosure may be included in the processors 11 and 21 or stored in thememories 12 and 22 so as to be driven by the processors 11 and 21.

The processor 11 of the transmitting device 10 performs predeterminedcoding and modulation for a signal and/or data scheduled to betransmitted to the outside by the processor 11 or a scheduler connectedwith the processor 11, and then transfers the coded and modulated datato the transceiver 13. For example, the processor 11 converts a datastream to be transmitted into K layers through demultiplexing, channelcoding, scrambling, and modulation. The coded data stream is alsoreferred to as a codeword and is equivalent to a transport block whichis a data block provided by a MAC layer. One transport block (TB) iscoded into one codeword and each codeword is transmitted to thereceiving device in the form of one or more layers. For frequencyup-conversion, the transceiver 13 may include an oscillator. Thetransceiver 13 may include N_(t) (where N_(t) is a positive integer)transmit antennas.

A signal processing process of the receiving device 20 is the reverse ofthe signal processing process of the transmitting device 10. Undercontrol of the processor 21, the transceiver 23 of the receiving device20 receives radio signals transmitted by the transmitting device 10. Thetransceiver 23 may include N_(r) (where N_(r) is a positive integer)receive antennas and frequency down-converts each signal receivedthrough receive antennas into a baseband signal. The processor 21decodes and demodulates the radio signals received through the receiveantennas and restores data that the transmitting device 10 intended totransmit.

The transceivers 13 and 23 include one or more antennas. An antennaperforms a function for transmitting signals processed by thetransceivers 13 and 23 to the exterior or receiving radio signals fromthe exterior to transfer the radio signals to the transceivers 13 and23. The antenna may also be called an antenna port. Each antenna maycorrespond to one physical antenna or may be configured by a combinationof more than one physical antenna element. The signal transmitted fromeach antenna cannot be further deconstructed by the receiving device 20.An RS transmitted through a corresponding antenna defines an antennafrom the view point of the receiving device 20 and enables the receivingdevice 20 to derive channel estimation for the antenna, irrespective ofwhether the channel represents a single radio channel from one physicalantenna or a composite channel from a plurality of physical antennaelements including the antenna. That is, an antenna is defined such thata channel carrying a symbol of the antenna can be obtained from achannel carrying another symbol of the same antenna. A transceiversupporting a MIMO function of transmitting and receiving data using aplurality of antennas may be connected to two or more antennas.

In the examples of the present disclosure, a terminal or UE operates asthe transmitting device 10 in UL and as the receiving device 20 in DL.In the examples of the present disclosure, a BS or eNB operates as thereceiving device 20 in UL and as the transmitting device 10 in DL.

The transmitting device and/or the receiving device may implement atleast one or more of the foregoing examples of the present disclosure incombination.

In one of the combinations of the proposals, a terminal for receivingdownlink signals in a wireless communication includes a receiver, atransmitter, and a processor. The processor may receive, from a basestation, a configuration of dynamic change to a predeterminedtransmission scheme related to a short transmission time interval(sTTI)-based downlink operation, when receiving the configuration of thedynamic change, detect a downlink control information format including afield related to the dynamic change, and when a value of the fieldindicates the predetermined transmission scheme, receive signals on adownlink data channel according to the predetermined transmissionscheme.

The configuration of the dynamic change may be configured per TTIlength. Further, the configuration of the dynamic change may beconfigured irrespective of a transmission mode related to the sTTI-baseddownlink operation.

The predetermined transmission scheme may be transmit diversity.

Further, the processor may report, to the base station, a terminalcapability as to whether the dynamic change to the predeterminedtransmission scheme is supported. The terminal capability reporting maybe defined per TTI length.

Further, the downlink control information format may schedule downlinkdata channels in a plurality of TTIs, and HARQ-ACK responses for thedownlink data channels in the plurality of TTIs may be transmittedindividually at timings corresponding to the respective downlinkchannels in the plurality of TTIs.

Further, the downlink control information format may schedule thedownlink data channels in the plurality of TTIs, and the HARQ-ACKresponses for the downlink channels in the plurality of TTIs may betransmitted by bundling or aggregation.

Further, the HARQ-ACK responses may be transmitted in resourcesdetermined by a lowest CCE index of the downlink control informationformat or resources spaced from resources linked to states of an ARIfield by a predetermined offset.

Further, a resource block set for monitoring the downlink controlinformation format, an aggregation level to be used in the resourceblock set for monitoring the downlink control information format, and/orthe number of monitoring candidates may be configured.

As described above, the detailed description of the preferred examplesof the present disclosure has been given to enable those skilled in theart to implement and practice the disclosure. Although the disclosurehas been described with reference to exemplary examples, those skilledin the art will appreciate that various modifications and variations canbe made in the present disclosure described in the appended claims.Accordingly, the disclosure should not be limited to the specificexamples described herein, but should be accorded the broadest scopeconsistent with the principles and novel features disclosed herein.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to wireless communication devicessuch as a terminal, a relay, a BS and the like.

The invention claimed is:
 1. A method for wireless communication by adevice, the method comprising: transmitting, to a network, devicecapability information indicating that a dynamic transmission-diversity(Tx-D) fallback operation for a short transmission time interval (sTTI)is supported by the device; receiving, through higher layer signaling,configuration regarding the dynamic Tx-D fallback operation for thesTTI; receiving downlink control information (DCI) including a specificfield set to one of a plurality of values including at least one valuefor the dynamic Tx-D fallback operation; and performing the dynamic Tx-Dfallback operation based on a value of the specific field in the DCI andthe higher layer signaled configuration.
 2. The method according toclaim 1, wherein the value of the specific field is interpreted based onthe configuration for the dynamic Tx-D fallback operation.
 3. The methodaccording to claim 1, wherein in a case where the configuration for thedynamic Tx-D fallback operation is related to first configuration, thevalue of the specific field is interpreted as an indication of a firstparameter, and wherein in a case where the configuration for the dynamicTx-D fallback operation is related to second configuration, the samevalue of the specific field is interpreted as an indication of a secondparameter.
 4. The method according to claim 3, wherein the firstconfiguration is configured to support two antenna ports, and the secondconfiguration is configured to support four antenna ports.
 5. The methodaccording to claim 3, wherein the first parameter and the secondparameter are related to antenna port information, respectively.
 6. Themethod according to claim 1, wherein the configuration regarding thedynamic Tx-D fallback operation is common for a first transmission mode(TM) and a second TM which are related to the sTTI.
 7. The methodaccording to claim 6, wherein the DCI related to either a first DCIformat used for the first TM or a second DCI format used for the secondTM.
 8. The method according to claim 7, wherein in the reception of theDCI: in a case where the device is configured with the first TM, thedevice receives the DCI by assuming that the DCI is related to the firstDCI format, and in a case where the device is configured with the secondTM, the device receives the DCI by assuming that the DCI is related tothe second DCI format.
 9. The method according to claim 1, wherein thespecific field is an existing field of the DCI, the existing field beingreused for indicating the dynamic Tx-D fallback operation to the deviceconfigured with the higher layer signaled configuration.
 10. The methodaccording to claim 1, wherein a length of a single transmission timeinterval (TTI) is 1 millisecond (ms) and a length of a single sTTI isless than 1 ms.
 11. The method according to claim 1, wherein the sTTI isrelated to a subslot, and a transmission time interval (TTI) is relatedto a subframe.
 12. The method according to claim 1, wherein the devicesupports a transmission time interval (TTI)-based operation in additionto the sTTI-based operation.
 13. The method according to claim 1,wherein the performing of the dynamic Tx-D fallback operation is relateto reception of downlink data through a downlink data channel.
 14. Themethod according to claim 1, wherein the device receives the DCI byperforming blind decoding of a sTTI-based physical downlink controlchannel (sPDCCH).
 15. A non-transitory processor readable mediumrecorded thereon at least one program code for executing the methodaccording to claim
 1. 16. A device for wireless communication, thedevice comprising: a memory configured to store instructions; and aprocessor configured to perform operations by executing theinstructions, the operations comprising: transmitting, to a network,device capability information indicating that a dynamictransmission-diversity (Tx-D) fallback operation for a shorttransmission time interval (sTTI) is supported by the device; receiving,through higher layer signaling, configuration regarding the dynamic Tx-Dfallback operation for the sTTI; receiving downlink control information(DCI) including a specific field set to one of a plurality of valuesincluding at least one value for the dynamic Tx-D fallback operation;and performing the dynamic Tx-D fallback operation based on a value ofthe specific field in the DCI and the higher layer signaledconfiguration.
 17. The device according to claim 16, further comprising:a transceiver configured to transmit or receive a wireless signal undercontrol of the processor, and wherein the device is a user equipmentconfigured to perform 3rd generation partnership project-based wirelesscommunication.
 18. The device according to claim 16, wherein the deviceis an application specific integrated circuit (ASIC), or a digitalsignal processing device.
 19. A method for wireless communication by abase station (BS), the method comprising: receiving, from a device,device capability information indicating that a dynamictransmission-diversity (Tx-D) fallback operation for a shorttransmission time interval (sTTI) is supported by the device;transmitting, to the device through higher layer signaling,configuration regarding the dynamic Tx-D fallback operation for thesTTI; transmitting, to the device, downlink control information (DCI)including a specific field set to one of a plurality of values includingat least one value for the dynamic Tx-D fallback operation; andperforming the dynamic Tx-D fallback operation based on a value of thespecific field in the DCI and the higher layer signaled configuration.20. A base station (BS) for wireless communication, the BS comprising: amemory configured to store instructions; and a processor configured toperform operations by executing the instructions, the operationscomprising: receiving, from a device, device capability informationindicating that a dynamic transmission-diversity (Tx-D) fallbackoperation for a short transmission time interval (sTTI) is supported bythe device; transmitting, to the device through higher layer signaling,configuration regarding the dynamic Tx-D fallback operation for thesTTI; transmitting, to the device, downlink control information (DCI)including a specific field set to one of a plurality of values includingat least one value for the dynamic Tx-D fallback operation; andperforming the dynamic Tx-D fallback operation based on a value of thespecific field in the DCI and the higher layer signaled configuration.